1. Field
The following description relates to a semiconductor device and a method for manufacturing the same, and to, for example, a stepped gate insulating layer MOSFET semiconductor device used in a level shifter block of a display driver IC and a method for manufacturing the double diffused MOS (DMOS) semiconductor device.
2. Description of Related Art
An enhancement driver depletion load metal oxide semiconductor device is a device in which a gate electrode of a load is connected to an output terminal by forming a driver in an enhancement type arrangement and the load in a depletion type arrangement in an inverter gate of a metal-oxide-semiconductor field-effect transistor (MOSFET). Since a metal-oxide-semiconductor (MOS) transistor as the load has constant-current characteristics, the DMOS device is widely used in a logic circuit due to excellent operating characteristics.
A conventional DMOS device includes an individual high-voltage device (HV device) and/or an individual medium-voltage device (MV device) having a large size and a low drain current in order to convert a low voltage (LV) into a medium voltage (MV) or a high voltage (HV). However, owing to insufficient drain current, it is difficult to drive the medium-voltage device or the high-voltage device by using a low voltage gate input. Thus, when a finger type MOS device in which a width is increased is used, there is a problem in that a size of a chip is reduced to cause a bottleneck phenomenon.
Further, because channel length modulation is not good in a level shifter block, it is difficult to secure a stable driving power. That is, the medium-voltage device or the high-voltage device is used when a low-voltage input is increased to a medium-voltage output or a high-voltage output in the level shifter block, and when a low-voltage gate voltage input is applied, since the drain current is low and the channel length modulation is not good, it is difficult to secure the stable driving power.
Patent Literature 1: U.S. Pat. No. 6,492,678.